Uber really should provide some sort of cost breakdown on your previous rides. (They provide quotes, but not itemized receipts.) But at least you can get a sense for how much they charge on their website.
Lyft, hilariously, doesn't tell you how much they charge! At all! What on Earth is their thinking behind that? Is it miles? Minutes? Am I charged based on my Klout score? It's a total mystery to me.
I hate taking cabs, but at least their pricing is 100% transparent.